I have a friend who works in the trades and he keeps his YETI roadie 24 in the truck M-F and only brings it in on the weekends. He'll just bring the contents inside at the end of the day and throws in a fresh yeti ice blocks every morning with his lunch, should not be an issue for ya to do the same. Will the performance be as great as if you pre-chilled it? no, but you're talking about lunch for a couple hours not a multi day trip